Interesting. Japanese Beetles do not visit the area and I have not noticed beetles of any types munching on them so I would try taking a picture and identifying the "culprit" so you can then apply appropriate countermeasures on the non-hydrangea plants. However, if the damage is slight, I would let them be. The only striped one that I know is the striped cucumber beetle.

By the way, you can take the picture to a local nursery (or capture one) and see if they can identify for you too. Try NorthHaven Gardens and/or Nicholson Hardie. Request to talk to someone who know and can identify insects.

FYI:

http://www.texasento.net/beetles.htm

This post was edited by luis_pr on Thu, May 15, 14 at 23:20

Some bugs are just there to eat dead stems. For example, there were sow bugs (land crustaceans) on the crowns of my macs doing just that - which was a signal to remove what came to be all old wood, as it was dead, had exfoliated the bark, and was beginning to rot.